Abstract: Regenerative medicine largely relies on cell-based therapy for treatment of degenerative diseases such as diabetes, heart failure and Parkinson's disease. Embryonic stem cells and recently established induced pluripotent stem cells will be able to contribute significantly in generating a renewable source of transplantable, fully functional cells. In spite of diverse efforts in deriving mature cellular phenotypes from these pluripotent cell types, what is lacking is a thorough understanding of the mechanism governing differentiation and lineage commitment of these pluripotent cells, hence resulting in incremental advancement of the field. My objective is to address the complex differentiation process from a completely different approach, which will have the potential to shift paradigms in regenerative medicine and stem cell bio-engineering as a whole. The objective of the proposed research is to develop an insightful mechanistic understanding of the process of differentiation through an integrated experimental and theoretical approach organized around three basic questions:(1) How does the transcription factors interact in controlling and deciding on a cell lineage ? (2) How do environmental perturbations influence these networks towards desired lineage? (3) How do gene and protein networks operating at the cellular level govern the tissue functionality at the systems level? These questions will be addressed in a system of embryonic stem cells differentiating to pancreatic islets, using a bottom-up approach where molecular level information will be integrated to predict tissue level functionality. Successful completion of this project will directly impact cellular therapy based regenerative medicine, and will pave way for mechanistic understanding of disease progression and potential therapeutic intervention. Public Health Relevance: Over 200 million people worldwide are affected by diabetes. Islet transplantation provides an attractive solution to diabetes, but is severely restricted by availability of donor pancreas. We propose to generate a mechanistic understanding in deriving functional islet cells from embryonic stem cells. This work will lead to generation of functional cell types which will directly improve public health by enabling increased number of transplantations.